This invention relates to semiconductor devices. More particularly, it relates to a package for a semiconductor device which is easily mountable on a printed circuit board.
Various schemes have been employed to package semiconductor devices. One of the most widely accepted schemes is the dual in-line package (DIP). Briefly, the DIP has a plurality of leads extending from both sides of an elongated rectangular body. The leads are bent so that they project downwardly to form a plurality of linear connector pins bounding the body of the package parallel to its side portions. The leads are generally soldered into corresponding holes in a printed circuit board in order to make external electrical connection to other devices. While the DIP has proved satisfactory in many applications, it has its drawbacks when it is realized that the package may have to be removed from the printed circuit board for various reasons. In order to remove the DIP from the printed circuit board, one must unsolder all of the leads. This of course is a time consuming operation which also requires access to a heat source such as a soldering iron. Furthermore, this can result in permanent damage to the printed circuit board.
In those applications where the package may foreseeably need to be removed from the printed circuit board, other packaging schemes have been suggested. For example, the semiconductor device has been mounted in a leadless-type package. Unlike the DIP, the leadless package does not have discrete leads extending from its main body portion. Accordingly, an intermediate connector is required to interface it with the printed circuit board. One of such connectors, as well as a leadless-type package, is disclosed in U.S. Pat. No. 3,771,109 Bruckner et al. Therefore, while the leadless package permits one to remove it from the printed circuit board, for example in order to replace a faulty semiconductor device, it necessarily requires an intermediate connector in order to make external electrical connection to other devices on the board. Unfortunately, these intermediate connectors tend to be expensive and may not provide reliable electrical connection to the conductors on the printed circuit board. This reduced reliability is due to the fact that multiple interfaces are used to provide the electrically conductive path between the device and the printed circuit board. Each pad on the leadless package is interfaced with a contact element in the connector, with the contact element, in turn, interfaced with the conductors on the circuit board. Each interface is a potential source of an unreliable connection.